Osteopontin-Enhanced Autophagy Attenuates Early Brain Injury via FAK–ERK Pathway and Improves Long-Term Outcome after Subarachnoid Hemorrhage in Rats

Abstract

Osteopontin (OPN) enhances autophagy, reduces apoptosis, and attenuates early brain injury (EBI) after a subarachnoid hemorrhage (SAH). A total of 87 Sprague–Dawley rats were subjected to sham or SAH operations to further investigate the signaling pathway involved in osteopontin-enhanced autophagy during EBI, and the potential effect of recombinant OPN (rOPN) administration to improve long-term outcomes after SAH. Rats were randomly divided into five groups: Sham, SAH + Vehicle (PBS, phosphate-buffered saline), SAH + rOPN (5 μg/rat recombinant OPN), SAH + rOPN + Fib-14 (30 mg/kg of focal adhesion kinase (FAK) inhibitor-14), and SAH + rOPN + DMSO (dimethyl sulfoxide). Short-term and long-term neurobehavior tests were performed, followed by a collection of brain samples for assessment of autophagy markers in neurons, pathway proteins expression, and delayed hippocampal injury. Western blot, double immunofluorescence staining, Nissl staining, and Fluoro-Jade C staining assay were used. Results showed that rOPN administration increased autophagy in neurons and improved neurobehavior in a rat model of SAH. With the administration of FAK inhibitor-14 (Fib-14), neurobehavioral improvement and autophagy enhancement induced by rOPN were abolished, and there were consistent changes in the phosphorylation level of ERK1/2. In addition, early administration of rOPN in rat SAH models improved long-term neurobehavior results, possibly by alleviating hippocampal injury. These results suggest that FAK–ERK signaling may be involved in OPN-enhanced autophagy in the EBI phase after SAH. Early administration of rOPN may be a preventive and therapeutic strategy against delayed brain injury after SAH.

Osteopontin as a candidate of therapeutic application for the acute brain injury

“…47 Accumulating evidence has demonstrated that OPN plays a significant role in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and multiple sclerosis, 26,27,48 as well as acute brain injury including TBI, stroke, and hypoxia-ischaemia brain injury. [49][50][51][52] Different acute brain injury models share many common features and processes within the pathophysiology. To date, most studies suggest a neuroprotective role of OPN in these neurological diseases.…”

“…116,117 Emerging studies suggest that OPN enhances autophagy and reduces apoptosis after experimental SAH through FAK signalling, resulting in the attenuation of early brain injury and improvement of long-term outcome. 51…”

Omi inhibition ameliorates neuron apoptosis and neurological deficit after subarachnoid hemorrhage in rats

“…Abnormal autophagy facilitates caspase-dependent neuronal apoptosis (Chung et al 2018). Enhancement of autophagy ameliorates neuronal apoptosis and subsequent neurological deficits after SAH in rats (Shao et al 2016;Sun et al 2019). By contrast, mitophagy-induced oxidative stress promotes neuronal death after SAH (Zhang et al 2019).…”

Kai-Xin-San Attenuates Doxorubicin-Induced Cognitive Impairment by Reducing Inflammation, Oxidative Stress, and Neural Degeneration in 4T1 Breast Cancer Mice

“…The left hemispheres were removed from brains and fixed in 4% paraformaldehyde for 24 hours and then incubated in 30% sucrose for 48 hours. Hippocampal coronal sections 16 μ m thick were taken using a Thermo NH50 cryostat, and 0.5% crystal violet was used for Nissl staining as in the previous study [ 30 ]. The morphological changes of neurons in the different positions of the hippocampus were observed under a light microscope at 200x magnification by two independent observers.…”